The present invention relates to a semiconductor device, and more particularly to a digital-to-analog converter (DAC).
A DAC is a device that converts a digital signal into an analog signal and is widely used in most electronic applications. A source driver of a thin film transistor-liquid crystal display (TFT-LCD) panel performs a digital-to-analog conversion. Thus, a DAC is essentially used in the source driver and has a great influence on display characteristics.
A conventional 6-bit or 8-bit source driver has used a resistor-string DAC. The resistor-string DAC is widely used in most source drivers because it has a good monotonicity and a good output characteristic.
A gray scale of a TFT-LCD system increases from 8 bits to 10 bits. When a typical resistor-string DAC extends to 10 bits, it still exhibits a good output characteristic, but occupies a very large area. For example, if 2 bits increase in the gray scale of the resistor-string DAC, the area of the DAC increases about four times.
Accordingly, a variety of DACs have been proposed for a source driver of a TFT-LCD having a high gray scale of 10 bits or more. A representative DAC is a charge-redistributed DAC using two capacitors. The charge-redistributed DAC can solve the increase of the area but has a poor output characteristic. Further, the yield of the DAC may decrease because of the use of the capacitors that are sensitive to variations in a manufacturing process.